1. Description of Related Art
Not Applicable
2. Field of the Invention
The present invention relates to mobile communications systems, and more specifically, to addressing the situation when features associated with a roaming mobile subscriber are not supported by the serving location register in a visited network.
FIG. 1 illustrates a wireless communication system in accordance with the Global System for Mobile communication (GSM) standard. The GSM standard is designed to provide a uniform interface which allows mobile communication subscribers of various countries to operate their mobile devices regardless of the current location of the mobile subscriber. A mobile subscriber typically has a subscription with a network which is designated as the mobile subscriber's home public land mobile network 110 (HPLMN). The HPLMN 110 has a home location register (HLR) 115 which contains, among other things, various information regarding the services provided to the mobile subscriber. When a mobile subscriber roams into a different network, which is referred to as a visited public land mobile network 120 (VPLMN), the VPLMN requires certain data regarding the mobile subscriber's subscription. The data regarding the mobile subscriber's subscription is also known as the mobile subscriber's profile. The mobile subscriber's profile is transferred from the HLR to a visitor location register (VLR) in the VPLMN 120.
In a GSM system mobile subscriber data is stored within the VLR that is associated with the mobile services switching center (MSC) that currently serves the mobile subscriber in order to reduce internetwork signaling between VLRs and HLRs. The decentralization of the VLRs within a GSM system (i.e., each MSC being equipped with a VLR) reduces intranetwork signaling as well. So, for example, if the mobile subscriber is roaming in an area of the VPLMN 120 which is controlled by the MSC/VLR 130, the HLR 115 will transfer the mobile subscriber's profile to MSC/VLR 130. Similarly, if the mobile subscriber is roaming in an area controlled by MSCNLR 135, the HLR 115 will transfer the mobile subscriber's profile to MSC/VLR 135. Although FIG. 1 illustrates the MSC/VLR as a single system node, one skilled in the art will recognize that the MSC and VLR can be implemented as separate system elements.
To increase the compatibility of GSM with other types of systems, it is anticipated that future versions of the GSM standard, also called Universal Mobile Telecommunications System (UMTS), will incorporate elements of other mobile communications systems. For example, the Japanese Personal Digital Cellular (PDC) system includes a system node which is used to reduce internetwork signaling known as a gateway location register (GLR). FIG. 2 illustrates an exemplary mobile communications system in accordance with the PDC system. Like a GSM system, a home network 210 includes an HLR 215 which contains the mobile subscriber's profile. When a mobile subscriber roams into a visited network 220 the mobile subscriber's profile is transferred to GLR 225. In GSM terms, the GLR can be described as a VLR for all subscribers roaming from other networks. Hence, only one GLR is needed for each network.
FIG. 3 illustrates an exemplary UMTS system which incorporates the GLR of the PDC system. When a mobile subscriber of HPLMN 310 roams into VPLMN 320, the HLR 315 will transfer the mobile subscriber's profile to GLR 325. Then, depending upon which area within the VPLMN 320 the mobile subscriber is roaming, the GLR 325 will transfer the mobile subscriber's profile to the respective MSC/VLR 330, 335 or 340. The introduction of the GLR 325 into a GSM/UMTS system reduces internetwork signaling because once the mobile subscriber roams into VPLMN 320, the HLR will only need to transfer the mobile subscriber's profile to GLR 325. GLR 325 will be responsible for transferring the mobile subscriber's profile to the proper MSC/VLR within VPLMN 320 as the mobile subscriber travels around the VPLMN 320.
The protocol used by GSM/UMTS systems for transferring data between VLRs and HLRs is the mobile application part (MAP). Since GLRs are optional elements within the UMTS system, MAP procedures should be completely independent of the presence or absence of GLRs in a system. Accordingly, by using an HLR interface towards the VLRs and a VLR interface towards the HLRs, the GLR should be completely transparent. However, in a system which includes a GLR where the different MSC/VLR nodes support different sets of supplementary services, the indications of this to the HLR in the home network becomes a problem. A similar problem occurs if some MSC/VLR nodes support regional subscription restrictions while others do not, or if different MSC/VLR nodes support different phases of customized applications for mobile network enhanced logic (CAMEL). CAMEL allows wireless systems to provide intelligent network services similar to those provided by wired networks such as the public switched telephone network. The same kind of problem is applicable when different bearer services and teleservices are supported, and when the support for operator determined barring varies between different MSC/VLR nodes. A similar problem occurs when the entire MSC area is restricted for a certain mobile subscriber for some MSC/VLRs but not restricted for other MSC/VLRs. For ease of explanation supplementary services, support for regional subscription restrictions, support for different phases of CAMEL, bearer services and teleservices are referred to herein as features.
FIG. 4 illustrates an exemplary signaling diagram of conventional MAP procedures for handling the situation when a serving MSC/VLR does not support at least one of the features associated with a subscriber. When a mobile subscriber enters an area controlled by an MSC/VLR, the mobile subscriber's device will send a location update request to the serving MSC/VLR. The serving MSC/VLR will then send a MAP_UPDATE_LOCATION message to the HLR associated with the roaming mobile subscriber. Triggered by the MAP_UPDATE_LOCATION message from the serving MSC/VLR the mobile subscriber's HLR initiates the framed MAP_INSERT_SUBSCRIBER_DATA procedure to transfer relevant mobile subscriber data to the serving MSC/VLR.
FIG. 5 illustrates a portion of an exemplary MAP_INSERT_SUBSCRIBER_DATA message which is sent from the HLR to the serving MSC/VLR. The MAP_INSERT_SUBSCRIBER_DATA message includes the SS Data List parameter 505, which indicates the set of supplementary services that are subscriber to by the concerned mobile subscriber, as well as provides necessary data for these supplementary services. If regional subscription restrictions apply for the concerned mobile subscriber, this is indicated in the Regional Subscription Data parameter 510. The MAP_INSERT_SUBSCRIBER_DATA message from the HLR also includes a Bearer Service List parameter 515 and Teleservice List parameter 520 indicating the bearer services and the teleservices that are subscribed to by the concerned mobile subscriber. If operator determined barring applies to the concerned mobile subscriber, this is indicated in the Operator Determined Barring General Data parameter 525, provided that the Subscriber Status parameter in the MAP_INSERT_SUBSCRIBER_DATA message (not illustrated) is set to “Operator Determined Barring”. The MAP_INSERT_SUBSCRIBER_DATA message implicitly indicates the CAMEL phases required by the mobile subscriber's subscription by the presence or absence of the CAMEL capability handling information element in the optional capability set I (O-CSI) information element in the VLR CAMEL subscription Information parameter (not illustrated). The presence of the CAMEL capability handling information element indicates CAMEL phase 2 or higher is subscribed to by the mobile subscriber while the absence of the information element indicates that CAMEL phase 1 is subscribed to by the mobile subscriber.
Referring again to FIG. 4, the MSC/VLR determines whether the features associated with the parameters set in the MAP_INSERT_SUBSCRIBER_DATA message are supported by the MSC/VLR and sends a MAP_INSERT_SUBSCRIBER_DATA response message to the HLR.
FIG. 6 illustrates a portion of an exemplary MAP_INSERT_SUBSCRIBER_DATA response message. If any of the indicated supplementary services are not supported by the serving MSC/VLR, these supplementary services are indicated in the SS-Code List parameter 605. If regional subscription restrictions are not supported by the MSC/VLR or if the entire MSC area of the serving MSC is restricted by the regional subscription restrictions (thereby making the mobile subscriber unreachable) or if the parameter contains formatting errors or other data errors, the Regional Subscription Response parameter 610 is included in the MAP_INSERT_SUBSCRIBER_DATA response message indicating the cause of the problem. If either of the indicated bearer services or teleservices are not supported by the MSC/VLR, this is indicated in the Bearer Service List parameter 615 or the Teleservice List parameter 620, respectively. If the mobile subscriber is subject to barring not supported/not allocated by the MSC/VLR, this is indicated in the Operator Determined Barring parameter 625 in the MAP_INSERT_SUBSCRIBER_DATA response message to the HLR. Also included in the MAP_INSERT_SUBSCRIBER_DATA response message from the MSC/VLR to the HLR is the Supported CAMEL Phases parameter 630, indicating the CAMEL phases supported by the MSC/VLR.
Referring again to FIG. 4, the location update procedure is completed by the HLR sending a MAP_UPDATE_LOCATION response confirmation message.
FIG. 7 illustrates signaling in a UMTS system when a mobile subscriber moves from an area controlled by one MSC/VLR to an area controlled by another MSC/VLR in a VPLMN which uses a GLR. When the mobile subscriber, who is not yet registered in the GLR (i.e., not yet registered in the VPLMN) enters an area served by MSC/VLR1 the mobile subscriber's device sends a location update message (not illustrated) to the MSC/VLR1 requesting support. MSC/VLR1 sends a MAP_UPDATE_LOCATION message to the GLR of the VPLMN. Since the mobile subscriber is registering for the first time from this particular VPLMN, the GLR forwards the MAP_UPDATE_LOCATION message to the HLR associated with the mobile subscriber. In response the HLR sends a MAP_INSERT_SUBSCRIBER_DATA message to the GLR indicating features currently subscribed to by and/or applied to the mobile subscriber. This message is forwarded by the GLR to the serving MSC/VLR1 which returns a MAP_INSERT_SUBSCRIBER_DATA response message which is forwarded by the GLR to the HLR. The MAP_INSERT_SUBSCRIBER_DATA response message contains the indications of the features subscribed to by and/or applied to the subscriber which are not supported by this particular serving MSC/VLR. The location updating procedure is completed by the HLR sending a MAP_UPDATE_LOCATION response message to the GLR, which in turn, forwards the message to MSC/VLR1.
To reduce internetwork signaling, when a GLR is used in the visited network, a MAP_UPDATE_LOCATION message is sent to the HLR of a roaming mobile subscriber only upon the first location update request of a series of consecutive location update requests from the roaming mobile subscriber in the particular visited network. Accordingly, when the mobile subscriber subsequently moves to other MSC areas or other serving MSC/VLRs, the HLR is not informed of this move. Instead the MSC/VLR, such as MSC/VLR2, will send a MAP_UPDATE_LOCATION message to the GLR. The GLR will respond with a MAP_INSERT_SUBSCRIBER_DATA message to MSC/VLR2. MSC/VLR2 returns a MAP_INSERT_SUBSCRIBER_DATA response message. The GLR completes the location updating procedure by sending a MAP_UPDATE_LOCATION response message to MSC/VLR2 and performing a location cancellation procedure with MSC/VLR1. Accordingly, if MSC/VLR2 supports different features than those supported by MSC/VLR1, the HLR, which needs to have this information to provide such features, is not informed, since the location update messages are not forwarded by the GLR to the HLR.